One of the most important functions of the human skin is to provide a barrier of the body towards the environment. A wound caused by an injury or disease may be treated by the use of a bandage or wound dressing to promote healing by preventing infection and leakage from the wound. Dressings used for wounds are often provided with a self-adhering adhesive, also known as pressure-sensitive adhesive (PSA), which purpose is to adhere to the skin surrounding the wound and to fixate the dressing in a desirable position. Various adhesives are available for affixing medical products on the skin, some of the most common being encompassed by the terms acrylic adhesives, and hot melt adhesives, among others.
In order to ensure that a medical device such as a wound dressing remains in the same position after a certain time of use an adhesive having a strong adherence, e.g. an acrylic adhesive, may be used. However, in case that the medical device is to be attached directly on the skin, an acrylic based adhesive increases the risk for pain and damages to the skin when such medical device is to be removed from the skin, e.g. due to skin stripping.
There are a number of commercially available skin products “film forming barrier” products or “skin sealant” products that address the problem of skin stripping by providing a protective layer on the skin before applying a pressure-sensitive adhesive thereto. Such products typically contain a protective polymer dissolved into fast-drying carrier solvent which upon application to the skin evaporates off to leave a film of the protective polymer on the skin. Examples of such products include: Cavilon™ No Sting Barrier Film (3M) containing acrylic terpolymer in hexamethyldisiloxane, Skin Prep™ (Smith & Nephew) containing a butyl ester of polyvinyl/maleic anhydride copolymer in isopropyl alcohol, Shield Skin™ (Mentor) containing a modified polyester and acrylic resin in isopropyl alcohol; and Bard® Protective Barrier Film (Bard Medical) and AllKare™ Protective Barrier Wipe (Convatec) both containing n-butyl and iso-butyl methacrylate in isopropyl alcohol.
U.S. Pat. No. 5,948,400 discloses a method of applying a pressure-sensitive adhesive wound dressing and a water-based skin treatment composition including a water dispersible film-forming polyester resin, a polyol plasticizer, and water, wherein a coating of the liquid composition is applied to the skin adjacent a wound and allowed to form a dry film prior to applying a pressure sensitive dressing over the wound. The dried film bonds strongly to the pressure sensitive adhesive of the dressing but is relatively easily removed from the skin and thus serves to reduce the force needed to remove the dressing, i.e. the coating according U.S. Pat. No. 5,948,400 reduces the total adherence between the dressing and the skin.
U.S. Pat. No. 8,263,720 B1 discloses crosslinked siloxy-containing polymers and their inclusion in liquid adhesive materials that can be used as sacrificial coatings under more adherent materials for protecting skin and mucous membranes. The sacrificial coating is weakly adhesive and may therefore be removed without damaging the skin when the more adherent material is removed. Thus, the coating of U.S. Pat. No. 8,263,720 B1 also reduces the total adherence between the more adherent material and the skin. The polymers of U.S. Pat. No. 8,263,720 B1 are all acrylate- or vinyl-based polymers, i.e. consisting of an acrylate- or vinyl-based backbone, having siloxy-containing pendant groups to increase solubility in hexamethyldisiloxane and/or to crosslink said acrylate- or vinyl-based polymers, and the coating of U.S. Pat. No. 8,263,720 B1 may therefore be regarded as a skin sealant of the same kind as the previously mentioned Cavilon™ No Sting Barrier Film (3M).
Soft silicone gel adhesives are known in the art (see e.g. WO2009031948) to be very gentle on the skin, in contrast to harder adhesives e.g. acrylic adhesives. This is because a soft adhesive can follow the contours of the skin well thus giving a large contact surface area. Thus, although the actual adhesive force in each contact point of a silicone gel adhesive is less than that of an acrylic adhesive, the large surface area of contact achieved with a silicone gel affords a high overall adherence to the skin, whilst at the same time being skin-friendly, i.e. when a silicone gel adhesive is removed from the skin very few skin cells are removed due to the low adhesive force in each contact point, thus the above mentioned problem of skin stripping can be avoided.
Although a soft silicone gel adhesive generally has good adhesion to a skin surface, for some applications, for example when used in a dressing to be applied on areas which are difficult to dress due to the 3D shape thereof and/or areas which are affected by body movements e.g. sacrum, elbow and knee, there may be a need for a stronger adhesion to the skin.
Furthermore, a soft silicone gel adhesive does typically not adhere equally well to a polymeric surface such as a polyurethane film which may be a problem in case a medical devices is to be attached to an area including two different surfaces. For example, in case a second medical device is to be attached to a wound area where a first medical device is already attached, the adhesive area of the second medical device to be applied on top of the first medical device would cover both a skin surface e.g. around the first medical device and a polymeric surface e.g. backing layer of the first medical device.
In general the adhesiveness of a dressing may be improved by increasing the amount of adhesive. However, an increased amount of adhesive leads to an increased manufacturing cost as well as less comfort due to lower breathability and increased thickness of the dressing. Further, the total adherence between medical device including a pressure-sensitive adhesive and a surface may be improved by first applying a layer of an adhesive coating on the surface prior to application of the pressure-sensitive adhesive thereto, for example, a coating of a BIO-PSA® containing a silicone adhesive may be provided on the surface. However, due to the high tack of such coating there is a risk of undesirable adhesion of objects and the handling of such coating is therefore in general troublesome.
Hence, there is a need in the art to further improve the overall adherence of a medical device to the skin or to other medical devices, while avoiding the drawbacks outline above.